Method of making plastic foam laminates



Dec. 20, 1960 P. E. RoGGl ErAL Y 2,964,799

- METHOD oF MAKING PLASTIC FOAM LAMINATES Filed June'e, 1957 2 sheets-sheet 1 BY 4MM A BENI' Dec. Z0, 1960 P. E. RoGGl Erm..

METHOD OF MAKING PLASTIC FOAM LAMINATES Filed June e. 1957 2 Sheets-Sheet 2 .A GENT "12,964,799 'METHOD oFMAKlNo PLAs'TrcFFM t f LAMINATES h h `Porfirio E. Rggi,` New Hayennd Raymond A. Chartier,

United StatesA C.

Naugatuck, Conn., assignorszto UnitedStates Rubber Y i Company, `New York, NX., `a `corporation of New Jersey h f t,

Filed June '6,119s7,s jei.No. 664,062

, This invention relates to a methodof makingplastic foam laminates and more particularly it ,relates to a method involving calenderingajthin filmof thermopiastic materialcontaining a chemical 'jbilowingragentxonto `a backing sheet, and `subsequently' lh'loiving 'or expanding the film under such conditions that the filmhis not v`'nip- 't'uredbut retains thejfoamel structu fthus imparted.v

Plastic foams, specifically those based on :vinyl chloride resins, are conventionally' made by two major techniques,

'and fuse the fluid plastisol into a solid, form-sustaining mass. The other` general category of vinyl resin foaming method is illustratedby the socalled Elastomerrand Fay Foamer processes (U.S`.` Patents,2`,`666 ,036, Schwencke, January 12, 1954; 2,763,475, Dennis, September*V 18, 1956), in which an inert gas` is blown into a liuid plastisol mix and the mix is then metered out onto a'continuous belt prior to fusing. Y

In both of the foregoing processesthe only existing commercial 'v way,1} insofar as the present inventors are advised, fmaking a continuous vinyl foam involves casting a fluidl plastisol in the form' of `aslab or blanket, that is several inches thick after expansion, after V'which 'the slab may be split to various desired thicknesses. 'This process suffersv from a serious llimitation Vin that 'thin slabs cannot be economically castV directly, but can only be made by spitting thicker slabs. This is not only inconvenient, but lthe split pieces do not have a continuous skin on the surfaceand their utility is thereby limited because of reduced abrasionresis'tance and re- `fduced adhesion surface, and because the'surface is dif- `ficult, if not impossible, to clean. Such a surface also has an undesirable tendency lto absorb moisture.`

Accordingly, a principal object ofthe presentinven- "tion is to provide an improved method `of making Vthermoplastic resin foam laminates in the form Vof a thin sheet. Another object is the provision of a method adapted to the continuous production of -foam laminatesf'from resins such as vinyl resin. l

Still a further object' is toprovide a more economical and eicient process for making vinyl vfresin foam, that lends itself to variations, such as the production of'composite articles made up in part of vinyl resin foam.

The manner in which the invention realizes the foregoing 'objects, las `well as "additional vobjects and ladvan- Itages, will be made manifest in the following detailed description, which is intended to be read `vvith-iref'erence to the accompanying drawings, wherein:

ice

ifieation ofthe invention, showing a vinyl film talendered on to a fabric base; i h

Fig. 3 .is a similarv-ievvf the coated'fabrieof Fig. 2. after blowing f the vinylIin; l l Figs. 4 and5 ar'e'similar'to Fi`gs2 and 3, respectively, but 'show the`vinyl film 4applied to 'a metal base;

Fig. 6 is a purely"diagr'ammati'c representation of "a modification 'of the invention in which the plastic film is heated vat spaced 'intervals to form lan intermittently blown product; y i v Fig.' 7` is a diagrammatic ross-s'ectinal view of an operi' rolfm'ill in process f millingla 'solid plastic material at elevated4 temperatures in aceordancefwith an initial step of the'method of the invention; arid, Y p i Fig. `8 is a flow diagram feplr'esentingthe practice .of the invention.

lnv accordance Vvt/ith theV invention, `a thermoplastic resin composition which is solid 'in form ato'rdinaryftemperatures (a`s distinguished from a plastisol,fvvhich `is essentially a` fl'uidfor paste at ordinary temperatures.) having afusion point less than' T85 C., is fir'st milled (either in an internalrnixer or onfan open rllmill, or both) with azodicarbonamide, suitaby in amount of from about l0.5 to about 50`p`arts Vof, azodicarbonamide per 100 `parts ,of theresiri, to make a uniform mixture in which the vazodicarbonamide is' dispersed or 'dissolved in the resin in an undecomposed state. Generally, the thinner the film the lower the `concentration of thel blowing agent, Within the specified range. The temperature employed during such milling is less than would be required todecompose the azodicarbonamide. kThe solid, milled mass thus obtained is quite distinct from a pla'stisol.V Ina plastiso`, the resin exists Vlargely in particulate form, dispersed in a fluid medium (the plasticizer), the'resin being` at the'initial stage ungelled and unfused, and the composition is iiowable and non-self-supporting. In contrast, in the 'mill mix employed in the present invention, the resin is a un,itary,solid mass, rather than particulate, and the composition is 'non-'liowableandv self-supporting at ordinary temperatures.

"The milled mass is thereafter calendered into the form of a fi in or sheet, 'having a 'thickness of from 0&001 Yto 0.15 inch, undery such 'conditions'that the'resin becomes fused into a continuous, strong film or sheet. yThetemperature employed in such calendering operation is Vin any case less than C., and there is thus ,obtained a plastic sheet 'or filmcontaining the incorporated 'az/.odicarbonamide in an undeconiposed condition. This fused sheet, after cooling,A is firm and non-tacky and may-be wound up 'into "a roll, or transported or stored in any other convenient form, for an indefinite period. As long as the filmV is `not subjected vto elevated temperature Athe azodicarbonamide remains `undecompose'd,. and the film can be marketed as such `or handled in the same manner as a typical conventional plastic film. Y

The next essential'step in the method of the invention involves Vheating'the thus previously fused, calendered, solid film orsheetbriey to a temperature in excess of C. (suitably from about 190 to about'255 C), whereby the previously incorporated azodicarbonamide is decomposed within the plastic film, thereby liberating nitrogen gas which causes Vthe film to expand to at least several times its original thickness, and thereby producing a uniform, expandedV or foamed film of good physical properties. 'Perhaps the most surprising result of this procedure 4Vlies in the fact 'that the iilmdo'es not become ruptured or otherwise damaged or distorted,`and the's'ur-f .face` of thefb'lwn -film'fis 'essentially-continuous on bothsides. It is not believed that it could have been foreseen beforehand that such an essentially solid skin would be formed on each surface of the expanded film, even though the process is carried out at atmospheric pressure without any effort to confine or contain the surfaces of the film by means of platens or molds Yor similar confining means. The ability of the sheet or film prepared as described to be blown freely without disruption is believed to be a consequence of the fact vthat the film was previously fused during the calendering'operation, thereby imparting great strength to the film. 1t would appear thatvonce the sheet or film has been fused at a suiiicientl'y elevated temperature, as in the previously described calendering operation, it is possible thereafter to heat the `sheet brieliy to temperatures appreciably in excess of the fusion temperature without encountering a no strength condition. This ability of the previously' fused sheet Ato ,be heated to a temperature substantially in excess of its fusion temperature for a brief period of time, without suffering complete disintegration or melting, is taken adlvantage of in the present process when the sheet is subsequently heated to a temperature suiciently elevated to decompose the azodicarbonamide. The preferred thermoplastic resins employed in the 4invention are the vinyl chloride resins, in which category we. include homopolymers of vinyl chloride and the known copolymers of vinyl chloride, such as those obtained by copolymerizing vinyl chloride with a minor amount of one or more copolymerizable monomers, such as vinyl acetate, vinylidene chloride, diethyl maleate, etc. Other conventional thermoplastic resins that may be employed include polyethylene, and the commercial 'material known as Cycolac (believed to be a graft polymer of styrene and acrylonitrile on polybutadiene or GRS), etc. If desired, mixtures of resins may be used, or mixtures of resins with rubbery materials (e.g., polyvinyl chloride and/or styrene-acrylonitrile resin in admixture with GR-S or nitrile rubber). In such mixtures there may be included a phenolic resin, or other modifying ingredients, including fillers, pigments or other coloring 'matten stabilizers or antioxidants, ock, plasticizers or softeners, processing aids or lubricants, etc. The invention will be further described with particular emphasis on the use of vinyl resin, especially vinyl chloride resin.

The typical vinyl chloride resin compositions employed in the invention have a fusion or calendering temperature in excess of 150 C., and preferably in excess of 160 C. but not greater than 185 C. Resin compositions which fuse at such relatively highly elevated temperatures are capable of forming, by calendering at such relatively highly elevated temperatures, unusually strong films or sheets having good physical properties, and such films are well able to withstand without disintegration the subsequent blowing stage, which involves even more highly elevated temperatures. This is in contrast to resin compositions which have fusion temperatures substantially below 150 C., or which are calendered into sheets at temperatures substantially below 150 C. Films or sheets calendered at such relatively low temperatures are not in general of the same high quality and strength as those calendered at higher temperatures within the presently specified range of 150 C., and especially 160 to 185 C. Furthermore, such relatively easily fusible resin compositions do not in general produce satisfactory results in the present blowing step, which is carried out at temperatures of 190 C. to 255 C., because at such high temperatures the easily fusible resin compositions have little strength. Although we frequently include plasticizer in our resin composition, plasticizer is not mandatory (as distinguished from the plastisol processes), and it is a nnique feature of the present process that it is operative with rigid vinyl resin containing little or no plasticizer. In general, if we use any plasticizer at all we useless than would be required in the plastisol process.v Thus, in the plastisol process it is usually necessary toy compound the vinyl chloride resin with about parts by weight of plasticizer, per 100 parts of the vinyl chloride resin, whereas in the present process we prefer to use less plasticizer, usually not more than 80 parts, and preferably not more than 60 parts. The vinyl resin or partially compounded vinyl resin is typically'initiallyin the form of discrete piecesor particles,'such as a powdered or diced material. The mixture including lthe vinyl resin and blowing agent is worked, usually on an open roll mill (with or without previous working in an internal mixer). in a heated, plastic condition until a relatively homogeneous and at least partially fused coherent mixture is obtained, in whichrthe azodicarbonamide presumably exists in the form of fine, evenly distributed particles, or the azodicarbonamide may be dissolved at least partially, but in any case it is substantially uniformly distributed. The milled mixture is a solid, in which the original resin particles have generally lost their individual identity and have become fused together and in bulk it is a quite hard, and generally rigid .mass at ordinary temperatures.

Vself-supporting and non-tacky and has consider-able strength,.and the .original discrete particles of vinyl resin have lost all identity, if indeed they have not already done so during the previous milling step. The calendering temperature will in general be within the range of from C. to 185 C., and preferably 160 C. to 185 C., depending mainly on the particular grade of vinyl resin and the plasticizer content. Such temperatures are insufiicient to cause decomposition of the azodicarbonamide, this being an essential requirement of the calendering step. The calendered vinyl film containing the undecomposed azodicarbonamide has a thickness of from 0.001 to 0.15 inch.

The calendered film cools down quickly as it comes off the calender, and it may, if desired, be rolled up and stored or shipped just like conventional calendered film. There is no tendency for the previouslydfused film to stick to itself or to other objects and Vit be handled and processed extensively without harm, being a strong and stable material.

It is desired to emphasize that the blowing or expanding step in the present process is carried out in such a manner that the azodicarbonamide is decomposed with the liberation of gas, by application of heat, but the conditions are such that the vinyl sheet does not rupture or tear, but substantially retains the porous structure irnparted by decomposition of the blowing agent. This is accomplished by subjecting the calendered sheet to a temperature in excess of the decomposition temperature of the azodicarbonamide (viz., a temperature of from C. to 255 C.) and discontinuing the heating almost immediately, i.e., within a period of from 5 to 60 seconds from the time required for the sheet to attain the aforementioned decomposition temperature. The said 5 to 60 second time interval immediately follows the time when a specific temperature in the range of 190-255 C. is reached. In order for the film to attain the desired blowing temperature of 190 C. or higher, we usually expose the sheeting to a higher temperature, such as 216 C., for longer periods of time, sometimes as long as 10 minutes. By thus applying quickly the heat required to decompose the blowing agent, and almost immediately withdrawing the heat, it has surprisingly been found possible to effect the blowing or expansion without harm to the sheet, even though such decomposition temperature fusion temperature,:but instead seemingly, requires a f l definite dwell at or above its fusion,V temperaturefbeforc it will cease to support itself fand collapse. This seems to be true specifically of vinyl resin that has previously been fused (as in the preceding calendering operation), which fusion .results in a strong, integral `mass, that Fis not easily made fiuent by`subsequent heating. The invention `further takes advantage of the face "that if a high enough temperature is applied,v the azodicarbonamide apparently can be substantially decomposed within an interval of timeless than that required to change the vinyl film from a solid to a fluid condition, even though such ldecomposition `temperature appreciably exceeds the nominal fusion `temperature of the vinyl composition. Again, the effect appears to be made possible by the previous ydefinite fusion of the vinyl resin during the `preceding high-temperature calendering operation, which `fusion produces a strong coherent sheet` that resists subsequent efforts to rupture it. Quick withdrawal of the heat immediately fixes the blow structure in the sheet and there is thereafter no danger of collapse or rupture.

The method lendsl itself readily to continuous operation,

as will be `apparent from inspection o-f the accompanying drawing. In the drawing, the vinyl chloride resin mix (containing azodicarbonamide) previously prepared on.

a mill 11, with or without previous working in an internal mixer (not shown), is transferred to a calender 12, where it is formed at a temperature of 150 C. to 185 C. as a 'film 13 having a thickness of from 0.001 to 0.15 inch, all

as previously related. The film may be taken off the rcalender, cooled and wound into a roll (not shown) for :subsequent expansion (after any desired intermediate fabricating or processing steps have been performed), Ior the film may be lead directly into a heating oven 14 in which it is continuously expanded at a temperature of `from 190 C. to 255 C. and quickly withdrawn and i cooled by passing around cooling drums 15 in the form of a blown sheet 16 which can be wound up subsequently :into a roll 17, orif desired cut into suitable lengths (not rshown) or otherwise further shaped or processed.

NThe resulting thin sheet `or blanket of vinyl foam is unusualyvstrong and uniforlmyhaving substantially evenly distributed minute cells of substantially uniform size. Typically, the cells are mainly closed cells,rthat is they :are not interconnected. There is typically an impervious :skin on each side ofthe sheet. The foam can be sub- :stantially rigid, unlike the conventional foam derived ,from piastisols, which is never truly` rigid.

The advantages of this processare numerous. First of zall, the initial -lm or sheet can be made at a high production rate, in continuous length which are limited only `by convenience of handling. This new process allows one to produce foams from formulation having desirable properties, in a wide latitude of stiffness ranges and it is possible to employ nonmigratory formulations (i.e., vformulations substantially devoid of lsolvent-type or monomeric type plasticizer, which tends to migrate out aof the sheet over a period of time, to the detriment of the properties of the sheet, or to lthe detriment of bodies Vin contact with the sheet, such as adhesives). -By varying the resin formulation it is possible to make films or :sheets having good low temperature flexibility as well as Vhigh temperature resistance, and V'it is also possible to make non-infiammable films. Frequently such qualities or variations in the formulation are not feasible in the plastisol process, because of the essential requirement for .la large volun'e of solvent-typefplasticizer. The present base 26 (for example, by the method of Kiernan and Y Y sheetsor filin a're'maten'ally vless expensive'to ship and store than the conventional blown foams. f

YIn addition, this fused film or sheetlends itself to the inyri'ad of post-calendering operations available to vinyl iilm such as printing, combining with other vinyl films, metal, fabric, and wood, priorto the blowing. Thus, Fig. 2'shows ak laminate` of `calendered vinyl film 20; prepared as described above, except that it has been calendered directly onto the surface of a textile fabric base 21. kWhen'such laminate is subjected to the described blowing operation, the vinyl film 20 as sho'wn in Fig. 3 expands freelyY while remaining firmly adhered to the fabric base Z1. In place ofthe fabric base 21, we may employ any other fiexible base, such as a plastic sheet or film, leather, etc., on one or both sides of the laminate. Similarly, a vinyl resin film 25 as. shown in Fig. 4 may be adhered to` a r'igid base, such as a metal Fischer, U.S.A Patent 2,728,703,V December 27, "1955) after which the film may be blo'wn to the condition shown in Fig. 5, while still adhered'to such base. Prior tothe blowing step, the laminatef'may bey subjected `to postforming operations, as disclosedinPatent No. 2,728,703. Other rigid bases, such,as rigidfplastic sheets, 'may be substituted for the metal base, Ion one or both sides of the laminate. p

The present"calen`dered film also lendsitself tofnovel intermittent Vblowing to obtain ribbing or quilting effects. Thus, as shown in Fig. 6, a calendered sheet V30 prepared in accordance with the invention may be passedaround a heated drum 31, the surface of which'bears a desired raised design or pattern, such as parallel bars 32. The heated bars 32 thus Contact thesheet 30 at'predeterrnine'd localities 33, thereby heating such localities to Vblowing temperature and producing the effect illustrated. It will be seen that the sheet 30 thus yacquires.'spaced raised 6r blown areas-34, corresponding-to the localities that were contacted by the raised bars of the heated drum. Various :desired designs or patterns `may 'becreated 'on the iilrn in this manner.

Foamsof differentcolors and stiffnesses may be cornbined by laminating a plurality of appropriately formulated films, Ibefore or after the blowing step.v

Example An example of a vinyl formulation that lends itself to this process is the following:

5 Azodicarbonamide.

The above ingredients were prnmixed cold for 10 rhin'- utes by agitation in conventional internal mixing e'quipment. (The stabilizers mentioned are optional and can be replaced by other conventional lef. e.g. Modern'Plastics Encyclopedia, 1956, p. 354-357] stabilizers with equivalent results.) The pre-mix was then fluxed on a mill at about C. until a homogeneous lmass was'obtained. The mix was then calendered at a temprature of C. into a sheet 0.030 inch thick.v This sheet was non-tacky after cooling,. and was stable and could be rolled up'nd shippe'do'r stored indefinitely. Upon pass# ing throughaii ove'ri wherein the `sheet was exposed to a temperature "of "216 C. fora period of 7 minutes, liche' sheet expanded to a thickness of 0.120". The resulting foam was soft Vand pliable, and had a continuous skin on both. sides.' The cell structure was uniform and unicellular. The density of the foam was approximately 20 pounds per cubic foot, and it had a 100% modulus of 100 p.s.i. The tensile strength of the foam was 150 p.s.i., and the elongation at break was 200%.

It is desired to emphasize the criticality of selecting in the present process a blowing agent that dccomposes at a temperature of 190 C. or above. It is only by the selection of such a blowing agent that the desirable vinyl chloride resin compositions having a high fusion temperature can be employed successfully, and it is only by selection of such a blowing agent that the desired high calendering temperatures can be employed, without premature decomposition of the blowing agent. We have found that azodicarbonamide is an ideal blowing agent, for the foregoing reason, and also because of additional essential advantages. Azodicarbonamide does not form objectionable quantities of surface bloom which would interfere with post-calendering operations such as printing, heat sealing, or combining with other materials. Neither does azodicarbonamide produce objectional deep coloration which would severely limit the color shades possible in the foam. Of paramount importance also is the ability of azodicarbonamide to produce, in economical concentrations, a manifold expansion of the vinyl chloride resin film, to up to five or even more times its original thickness, the cell structure being remarkably fine and uniform, when the process is carried out under'the critical conditions described.

The foregoing results are in direct contrast to those obtained if it is attempted to carry out a similar process with other blowing agents, for example, with benzilmonohydrazon (van Gaver, U.S. Patent 2,586,887, February 26, 1952). The latter blowing agent decomposes at about G-160 C., thereby limiting one to the use of resin compounds that can be processed at temperatures substantially less than 150 C. Such cornpounds usually require low molecular weight resins and/or excessive quantities of plasticizer, and in general such compounds have definitely inferior heat resistance, inferior physical properties, inferior solvent resistance, and have other undesirable characteristics, in contrast to the resin compositions operable in the present process, which resin compositions in general have a fluxing temperature of from 150 to 185 C., and preferably 160 to 185 C.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

1. A method of making a laminated article having a layer of vinyl chloride resin foam attached to a sheet of base material comprising milling a solid vinyl chloride resin having a fusion temperature of 150 C. to 185 C. and a blowing agent having a decomposition temperature of at least 190 C., the resulting milled mixture being a unitary, solid, non-particulate mass which is non-fiowable and self-supporting at room temperature, calendering the said mass continuously into a thin, coherent film of indefinited length having a thickness of from 0.001 to 0.15 inch, the temperature during said calendering being within the range of 150 C. to 185 C. and being sufficient to fuse the resin so that the film thus produced is strong and inherently capable of being reheated briefiy in excess of fusion temperature without encountering a non-strength condition, the said film being applied to a sheet of base material, subsequently passing a running length of the resulting assembly of film and sheet of base material continuously through an oven wherein the assembly is heated to a film temperature of 190 C. to 255 C. at atmospheric pressure without confinement, said film temperature being maintained for a period of 5 to 60 seconds to decompose the blowing agent with liberation of gas and freely expand the film without disruption to form a uniform, blown sheet having at least several times the thickii'ess of the original film, such blown sheet having a continuous surface and being attached to said base, and immediately thereafter cooling the assembly.

2. A method of making a laminated article having a layer of vinyl chloride resin attached to a sheet of base material comprising continuously forming'a film of plasticized vinyl chloride resin containing a blowing agent having a decomposition temperature of at least 190 C., the said resin having a fusion temperature of C. to C., the said film being formed at a temperature within the range of 160 C. to 185 C. whereby the resin is thoroughly fused and the film is inherently capable of being subsequently reheated briefiy in excess of fusion temperature without encountering a no-strength condition, the 'said film being applied to a sheet of base material, subsequently passing a running length of the resulting assembly of film and sheet of base material continuously through an oven wherein the assembly is heated to a film Vtemperature of C. to 255 C. at atmospheric pressure without confinement, said film temperature being maintained for a period of 5 to 60 seconds to decompose the blowing agent with liberation of gas and freely expand the film without disruption to form a uniform, blown sheet of plasticized vinyl chloride resin having at least several times the thickness of the original film, such blown sheet having a continuous surface and being attached to the said base, and immediately thereafter cooling the assembly.

3. A method of making a laminated article having a layer of plasticized vinyl chloride resin foam attached to a sheet of base material comprising milling solid vinyl chloride resin, plasticizer for said resin, and azodicarbonamide as a blowing agent, the said resin having a fusion temperature of 150 C. to 185 C., the resulting milled mixture being a unitary, solid, non-particulate mass which is non-flowable and self-supporting at room temperature, calendering the said mass continuously into a thin, coherent film of indefinite length having a thickness of from 0.001 to 0.15 inch, the temperature during said calendering being Within the range of 150 C. to 185 C. and being sufficient to fuse the resin so that the film thus produced is strong and inherently capable of being reheated briefly in excess of fusion temperature without encountering a nostrength condition, the said film being applied to a sheet of base material, subsequently passing a running length of the resulting assembly of film and sheet of base material continuously through an oven wherein the assembly is heated to a film temperature of 190 C. to 225 C. at atmospheric pressure without confinement, said film temperature being maintained for a period of 5 to 60 seconds to decompose the azodicarbonamide with liberation of gas and freely expand the film without disruption to form a uniform, blown sheet of plasticized vinyl chloride resin having at least several times the thickness of the original film, such blown sheet having a continuous surface and being attached to said base, and immediately thereafter cooling the assembly.

4. A method of making a laminate of a plasticized vinyl chloride resin foam and a textile fabric base comprising continuously forming a film of plasticized vinyl chloride resin containing azodicarbonamide as a blowing agent on a running length of textile fabric base, the said resin having a fusion temperature within the range of 160 C. to 185 C., the said film being formed at a temperature within the range of 160 C. to 185 C. whereby the resin is thoroughly fused and the film is inherently capable of being subsequently reheated briefly in excess of fusion tempreature without encountering a no-strength condition, the said film having a thickness of from 0.001 to 0.15 inch, subsequently passing a running length of the resulting assembly of film and textile fabric base continuously through an oven wherein the assembly is heated to a film temperature of 190 C. to 255 C. at atmospheric pressure without confinement, said film temperature being maintained for a period of 5 to 60 seconds to decompose the azodicarbonamide with liberation of gas and freely expand the film without disruption to form a uniform, blown sheet of plasticzed rvinyl chloride resin having at least several times the thickness of the original film, such blown Sheet hav- `ing a continuous surface and being attached to said base, and immediately thereafter cooling the assembly.

5. A method of making a laminate of a plasticized vinyl chloride resin foam and a textile fabric base comprising milling solid vinyl chloride resin, plasticizer for said resin, and azodicarbonamide as a blowing agent, the resulting mixture being a unitary, solid, non-particulate mass which is non-flowable and self-supporting at room temperature and which has a fusion temperature of from 160 C. to 185 C., calendering the said mass continuously onto a running length of a textile fabric base in the form of a thin, coherent film of indefinite length having a thickness of from 0.001 to 0.15 inch, the temperature during said calendering being within the range of 160 C. to 185 C. and being sucient to fuse the resin so that the lm thus produced is strong and inherently capable of being reheated briefly in excess of the fusion temperature without encountering a nostrength condition, subsequently passing a running length of the resulting assembly of film and textile fabric base continuously through an oven wherein the assembly is heated to a lm temperature of 190 C. to 225 C. at atmospheric pressure without confinement, said lm temperature being maintained for a period of 5 to 60 seconds to decompose the azodicarbonate with liberation of gas and freely expand the film without disruption to form a uniform, blown sheet of plasticized vinyl chloride resin having at least several times the thickness of the original film, such blown sheet having a continuous surface and being attached to said textile fabric base, and immediately thereafter cooling the assembly.

References Cited in the file of thispatent UNITED STATES PATENTS 2,325,903 Blair et al Aug. 3, 1943 2,442,940 Staudinger et al. June 8, 1948 2,447,056 Cooper Aug. 17, 1948 2,525,965 Smith Oct. 17, 1950 2,576,749 Carpentier Nov. 27, 1951 2,740,991 Hess et al. Apr. 10, 1956 UNITED STATES PATENT oEEIcE CERTIFICATE OF CGRBECTION Patent No., 2,964,799 December 2o, 1960 Porfirio EIn Raggi et an It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below..

Column 5, line l5I for "ffice"l read fact line 27 for "blow" read blown; line 4l, for "leadm read led column 7, line 65, for "non-strength" read no=strength column 8v line 48, and column lOq line 4, for "2250 CJ each f occurrence, read 255o (3 -wo Signed and sealed this 7th day of November 1961,

i (SEAL) Attest:

IRNEST W. SWIDEE DAVID L. LADD Attesting Officer Commissioner of Patents USCOMM-DC 

1. A METHOD OF MAKING A LAMINATED ARTICLE HAVING A LAYER OF VINYL CHLORIDE RESIN FOAM ATTACHED TO A SHEET OF BASE MATERIAL COMPRISING MILLING A SOLID VINYL CHLORIDE RESIN HAVING A FUSION TEMPERATURE OF 150*C. TO 185*C. AND A BLOWING AGENT HAVING A DECOMPOSITION TEMPERATURE OF AT LEAST 190*C., THE RESULTING MILLED MIXTURE BEING A UNITARY, SOLID, NON-PARTICULATE MASS WHICH IS NON-FLOWABLE AND SELF-SUPPORTING AT ROOM TEMPERATURE, CALENDERING THE SAID MASS CONTINUOUSLY INTO A THIN, COHERENT FILM OF INDEFINITE LENGHT HAVING A THICKNESS OF FROM 0.001 TO 0.15 INCH, THE TEMPERATURE DURING SAID CALENDERING BEING WITHIN THE RANGE OF 150*C. TO 185%C. AND BEING SUFFICIENT TO FUSE THE RESIN SO THAT THE FILM THUS PRODUCED IS STRONG AND INHERENTLY CAPABLE OF BEING REHEATED BRIEFLY IN EXCESS OF FUSION TEMPERATURE WITHOUT ENCOUNTERING A NON-STRENGTH CONDITION, THE SAID FILM BEING APPLIED TO A SHEET OF BASE MATERIAL, SUBSEQUENTLY PASSING A RUNNING LENGTH OF THE RESULTING ASSEMBLY OF FILM AND SHEET OF BASE MATERIAL CONTINUOUSLY THROUGH AN OVEN WHEREIN THE ASSEMBLY IS HEATED TO A FILM TEMPERATURE OF 190*C. TO 225*C. AT ATMOSPHERIC PRESSURE WITHOUT CONFINEMENT, SAID FILM TEMPERATURE BEING MAINTAINED FOR A PERIOD OF 5 TO 60 SECONDS TO DECOMPOSE THE BLOWING AGENT WITH LIBERATION OF GAS AND FREELY EXPAND THE FILM WITHOUT DISRUPTION TO FORM A UNIFORM, BLOWN SHEET HAVING AT LEAST SEVERAL TIMES THE THICKNESS OF THE ORIGINAL FILM, SUCH BLOWN SHEET HAVING A CONTINUOUS SURFACE AND BEING ATTACHED TO SAID BASE, AND IMMEDIATELY THEREAFTER COOLING THE ASSEMBLY. 